Intermediate-depth earthquakes facilitated by eclogitization-related stresses

Junichi Nakajima, Naoki Uchida, Takahiro Shiina, Akira Hasegawa, Bradley R. Hacker, Stephen H. Kirby

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)

Abstract

Eclogitization of the basaltic and gabbroic layer in the oceanic crust involves a volume reduction of 10%-15%. One consequence of the negative volume change is the formation of a paired stress field as a result of strain compatibility across the reaction front. Here we use waveform analysis of a tiny seismic cluster in the lower crust of the downgoing Pacific plate and reveal new evidence in favor of this mechanism: tensional earthquakes lying 1 km above compressional earthquakes, and earthquakes with highly similar waveforms lying on welldefined planes with complementary rupture areas. The tensional stress is interpreted to be caused by the dimensional mismatch between crust transformed to eclogite and underlying untransformed crust, and the earthquakes are probably facilitated by reactivation of fossil faults extant in the subducting plate. These observations provide seismic evidence for the role of volume change-related stresses and, possibly, fluid-related embrittlement as viable processes for nucleating earthquakes in downgoing oceanic lithosphere.

Original languageEnglish
Pages (from-to)659-662
Number of pages4
JournalGeology
Volume41
Issue number6
DOIs
Publication statusPublished - 2013 Jun 1

ASJC Scopus subject areas

  • Geology

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